Backup broadband gets sold the same way to everybody, usually with a story about disaster. The honest answer is that some businesses genuinely cannot afford an hour offline, and others could lose a morning and barely notice. The useful question is not whether backup is a good idea in the abstract. It is what an outage actually costs you, and which of the three levels of protection is worth paying for.
The 30-second version
- Work out the cost of an hour offline first. Everything else follows from that number.
- There are three levels, from a mobile SIM that takes over automatically to a second dedicated line with a repair guarantee.
- Most businesses want the cheapest level, and for most of them that is the right answer.
- A backup that shares a path with your main line is not a backup. This is the most common and most expensive mistake.
- Remember the phones and the card machine. If your voice runs over the internet, an outage takes the phones with it.
On this page
Start with what an hour offline actually costs
This sounds like a finance exercise and it takes about five minutes. You do not need a precise figure, just the right order of magnitude, because the answer changes which level you buy.
Add up, for one hour in a normal working day:
- Staff who cannot do their job. Not everyone stops, but the ones on cloud systems, email or phones do. Take their hourly cost and be honest about how many.
- Orders, bookings or payments you cannot take. For a shop, a restaurant or anyone taking card payments, this is the big one and it is immediate.
- Calls you do not answer. If your phones run over the internet, they go down too. A missed call from a new customer is not recovered later, it goes to whoever answers next.
- The work that still has to be done afterwards. An outage rarely removes work, it just moves it to the evening.
A four person office where people can get on with other things might land somewhere around a hundred pounds an hour. A busy restaurant on a Friday night, or a contact centre, can be many times that. Our piece on the cost of an hour offline works through it properly if you want the longer version.
Who genuinely needs a backup, and who does not
Nobody enjoys being told they need something they do not. Here is the rough split as we see it:
| Situation | Realistic verdict |
|---|---|
| You take card payments or bookings in person | Yes, and it pays for itself the first time it is used |
| Your phones run over the internet | Yes. An internet fault becomes a phone fault, which customers notice immediately |
| You run on cloud systems all day | Yes, at the basic level at least |
| You have staff working on site who depend on remote access | Yes, because the cost lands on several people at once |
| Mostly email and documents, small team, flexible day | Probably not. You can lose a morning and catch up |
| You already have a leased line with a strong SLA | Maybe not a second line, but check what the SLA actually promises |
That last row matters. A leased line with a four hour fix is not the same as no outage, it is a promise about how long one lasts. If four hours offline is genuinely unacceptable, you still need something alongside it.
The three levels, and what each gives you
| Level | What it is | Suits |
|---|---|---|
| Mobile failover | A 4G or 5G SIM in the router that takes over automatically when the main line drops | Most businesses. Cheap, quick to fit, and shares nothing with your fixed line |
| A second fixed line | A separate broadband circuit, ideally from a different supplier on a different route | Heavier use where a mobile connection would not carry the full load |
| Leased line plus backup | A dedicated line with a repair guarantee, with one of the above behind it | Businesses where being offline is genuinely not survivable |
What we would not sell you
A second broadband line that follows the same route into the building as the first. It looks like resilience on paper and costs real money every month, and a digger through the wrong duct takes out both.
The honest advice for most businesses is level one. A mobile SIM in a capable router is inexpensive, takes an hour to fit and covers the overwhelming majority of real outages, because most faults are in the fixed line or the local cabinet rather than everywhere at once. Level two and three are for cases where the numbers you worked out above justify them.
The backup that is not really a backup
This is the single most common problem we find when we look at an existing setup. A business has paid for two connections for years, in good faith, and they share something important.
The overlaps to check are the physical route into the building, the street cabinet, and the exchange. Two suppliers can still mean one cable in one duct, because most providers are reselling the same underlying network. A mobile SIM sidesteps almost all of it, which is a large part of why it is the usual recommendation.
Worth checking on an existing setup
If you already pay for a backup, it is worth having somebody confirm it is genuinely separate, and that it still works. We will look at what you have and tell you either way. Our guide to true network diversity covers where backups quietly overlap.
Do not forget the phones and the card machine
People think about backup in terms of the internet, then discover during the first outage that it took the phones with it. If your phone system is hosted, which almost all now are, it depends on the same connection.
That changes the sizing question. A backup line that carries email is not necessarily one that carries fifteen simultaneous calls plus card payments plus everyone reconnecting at once. It is worth saying out loud what has to keep working, because the answer is usually more than people first assume.
- Phones, if voice runs over the internet.
- Card payments, which fail in front of a customer.
- Anything with a fixed IP, because the address changes on a mobile backup unless the SIM is set up for it.
- Door entry, CCTV and alarms, if they report over the same connection.
How to choose without overbuying
- Put a number on an hour offline. Rough is fine. It decides everything after this.
- List what genuinely has to keep working, not everything you own. Usually phones, payments and a handful of systems.
- Start at level one unless the numbers clearly say otherwise. Mobile failover covers most real outages for a modest monthly cost.
- Check the backup is genuinely separate from your main line, whatever level you land on.
- Make sure it switches by itself. A backup somebody has to plug in is a plan, not protection. Our guide to how automatic failover works covers the technical side.
- Test it, then test it again in six months. An untested backup is an assumption.
Not sure which level you need?
Tell us what your business does on a normal day and what would hurt most if it stopped. We will tell you honestly whether you need a backup at all, and which level is worth paying for. We would rather say no than sell you a second line you will never use.